Short report: isolation and partial characterization of a Puumala virus from a human case of nephropathia epidemica in France.

Puumala (PUU) virus (Bunyaviridae: Hantavirus), the etiologic agent of nephropathia epidemica (NE), the mid form of hemorrhagic fever with renal syndrome, is enzootic in Europe and has been known to occur in France since 1983. We report the first isolation of PUU virus in France and western Europe from a case of NE acquired in France. The virus was isolated from a serum collected in the acute phase of the clinical course by successive blind passages in Vero E6 cells. Serologic typing using monoclonal antibodies confirmed the identity of the virus as PUU. The sequence of an 832-nucleotide fragment of the virus medium RNA segment obtained by the polymerase chain reaction (PCR) also classified it as a PUU virus. The sequence of this isolate from a human case in France is closely related to the sequence of a PUU virus obtained by the PCR from a German patient.

[Post-exposure antirabies vaccination. Early serological response to vaccine cultivated on VERO cells using a reduced 2-1-1 schedule]. / Vaccination antirabique après exposition. Réponse sérologique précoce au vaccin cultivé sur cellules VERO utilisé en schéma réduit 2-1-1.

OBJECTIVES: An abbreviated 2-1-1 schedule for post-exposure rabies vaccination would theoretically lead to more rapid production of specific antibodies than the classical schedule. We measured early serological response to the 2-1-1 schedule. METHODS: Patients consulting the antirabies centre of the Epinal hospital from June 1992 to June 1993 who had never been vaccinated and whose exposure history justified antirabies vaccination were included in this study. Fifty subjects were vaccinated with PVRV (purified vero rabies vaccine, Pasteur Institute) cultured on VERO (vervet monkey origin) cells using the abbreviated 2-1-1 schedule of 2 doses (0.5 ml = 2.5 IU/dose) on day 0 and 1 dose on days 7 and 21. Antirabies antibodies were assayed using the Platelia Rage immunoenzyme method (Diagnostic Pasteur) on day 21. Titres above 0.5 IU were considered to give protection and non-protected subjects were seen again on day 28 for a supplementary dose. RESULTS: Only 34 subjects (68%) had protective antibody titres on day 21, but by day 28, 48 (96%) had acquired immunity. In this study population, the age range was from 1 to 83 years and age over 30 years appeared to delay antibody formation. CONCLUSION: These findings emphasize the importance of initial antirabies immunoglobulins if short incubation in suspected and the need for serological follow-up if delayed antibody formation is suspected (subjects over 30).

[Rabies encephalomyelitis with myocarditis and pancreatitis. Report on a case recently imported into France]. / Encéphalomyélite rabique avec myocardite et pancréatite. Observation d'un cas récent importé en France.

We report the case of a 29 year-old man who died from rabies in France, following a dog-bite during a trip in Mexico. Although it was clinically suspected, the diagnosis was uncertain until he died because of digestive, cardiac and psychiatric misleading symptoms associated to the neurologic disorders. Post mortem diagnosis was based upon virological study in immunofluorescence on cerebral smears, viral isolation on cell-culture, and ELISA. It was confirmed by light microscopy examination which showed numerous Negri bodies, and ultrastructural study of the rhabdovirus in the central nervous system. Extranervous lesions, especially myocarditis and pancreatitis, were observed and their meaning is discussed. The physician is exceptionally confronted to the diagnosis of human rabies in France. Nevertheless, the lack of compulsory antirabic vaccination and the increase of touring in enzootic countries increase the risk of infection. As an intra vitam diagnosis in frequently lacking, the diagnosis of rabies infection needs a complete post mortem virological study as well as an histological and ultrastructural examination of the central nervous system.

Safety and immunogenicity of combined rabies and typhoid fever immunization.

The prevalence of rabies and typhoid fever in many developing countries poses a serious health hazard to travellers. The development of a combined immunization schedule would be advantageous. A study was performed on 104 adult volunteers using purified Vero cell rabies vaccine and Typhim Vi, a purified capsular polysaccharide, either separately or in combination. No significant difference was observed in immunogenicity or tolerance between the two groups. A 3-year follow-up study is planned.

Contribution to rabies prevention.

After the end of the Second World War, an outbreak of fox rabies invaded Europe. For the immunization of human populations and domestic animals against the risk of rabies transmitted by infected wild animals, it appeared necessary to replace the first generation of rabies vaccines (nerve tissue vaccines) by more potent and safer vaccines. The European vaccine manufacturers, in close collaboration with the research institutes engaged in rabies research, soon and quickly developed a second generation of rabies vaccines, produced in cell cultures including continuous cell lines grown in bioreactors of industrial scale. The third generation of rabies vaccines is already available: the vaccinia-rabies glycoprotein recombinant vaccine is presently applied on a large scale in some European countries for immunization of wildlife. The canarypox recombinant vaccine has already been considered and successfully tested for human immunization.

Rabies-specific production of interleukin-2 by peripheral blood lymphocytes from human rabies vaccinees.

Cell-mediated immunity induced by rabies vaccination was studied in humans by the determination of specific interleukin-2 (IL-2) production in a large number of donors (postexposure immunized patients and pre-exposure immunized laboratory workers). Peripheral blood lymphocytes (PBL) from 35 donors were tested for IL-2 production after in vitro stimulation by different rabies and rabies-related viruses. IL-2 responses were compared to antibody recognition of these different virus serotypes by sera from the same individuals. IL-2 was produced by PBL from more than 85% of donors after stimulation with inactivated and purified rabies viruses (IPRV) prepared from either Pittman Moore (PM) or Pasteur Virus (PV) strains. IL-2 was also produced by 65 and 45% of donor PBL stimulated with IPRV from the European Bat Lyssavirus (EBL) and Mokola (Mok) rabies-related virus strains respectively. No correlation was found between the production of IL-2 by PBL and the levels of virus neutralizing antibody (VNAb). Moreover, 50, 25 and 35% of donors produced IL-2 after stimulation of their PBL with ribonucleoprotein (RNP) from PV-, EBL- and Mok-viruses, respectively. These results obtained with a large number of human rabies vaccinees and using an assay specific to T-cell activation confirm the significant cross-reactivity of T-cell responses directed against rabies and rabies-related viruses. This study shows that IL-2 production could be used for the study of cell-mediated immunity and T-cell memory induced in humans by rabies vaccination.

Appraisal of rabies vaccine potency by determination of in vitro, specific interleukin-2 production.

The potency of different rabies vaccines was measured via cell mediated immunity (CMI) assessed by the production of interleukin-2 (IL-2) by CD4+CD8- lymphocytes. IL-2 production by splenocytes from mice immunized with various vaccines was measured following in vitro stimulation with antigens from different rabies and rabies-related strains. IL-2 production was specific, reproducible and correlated with the vaccine protective activity as determined by the pre-exposure NIH test. Our results suggest that measurement of IL-2 production could be used for the appraisal of rabies vaccine potency.

In vitro rabies vaccine potency appraisal by ELISA: advantages of the immunocapture method with a neutralizing anti-glycoprotein monoclonal antibody.

The replacement of the in vivo potency test (NIH test) for rabies vaccine evaluation by in vitro methods is at present discussed in many reports and also by WHO expert working groups. For this purpose, in vitro glycoprotein titration has been proposed. Among the different glycoprotein assays, we have studied two ELISA methods (immunocapture and direct plate coating with the antigen to be tested) using neutralizing mono- and polyclonal antibodies. In our view, the immunocapture method based on the use of a neutralizing monoclonal anti-glycoprotein antibody seems to be a convenient tool for the determination of the in vitro potency of rabies vaccine and of the products corresponding to the different steps of their production process.

Enhancement of interleukin-2 activity by liposomes.

The present report demonstrates that liposomes increase the interleukin-2 (IL-2) dependent proliferation of cytotoxic T-lymphocyte line (CTLL) cells used for the measurement of IL-2 activity. This effect was better observed with suboptimal doses of IL-2 and low concentrations of lipids. The increased IL-2 dependent proliferation is not due to a direct effect of liposomes on CTLL cells but rather to an interaction between IL-2 and liposomes. An interaction between IL-2 and components of fetal calf serum is also demonstrated. The results indicate that liposomes may interfere with IL-2 bioassay but also show the possibility of potentiating IL-2 activity for therapeutic purposes.

From rabies to rabies-related viruses.

Antigenic differences between rabies virus strains characterized with monoclonal antibodies presently define at least four serotypes within the Lyssavirus genus of the Rhabdoviridae family: classical rabies virus strains (serotype 1), Lagos bat virus (serotype 2), Mokola virus (serotype 3) and Duvenhage virus (serotype 4). The wide distribution of rabies-related virus strains (serotypes 2, 3 and 4) and above all, the weak protection conferred by rabies vaccines against some of them (principally Mokola virus) necessitates the development of new specific vaccines. We first determined the complete nucleotide sequence of a rabies virus strain of serotype 1 (Pasteur virus) and characterized the structure of the viral genes and their regulatory sequences. We then extended this study to the Mokola virus genome. Five non-overlapping open reading frames were found in both viruses and had similar sizes and positions in both. Similarities were also found in the mRNA start and stop sequences and at the genomic extremities. Comparison of both genomes helps to analyze the basis of the particular antigenicity of these two serotypes. The sequence homology in the region coding for the viral glycoprotein was only 58% between the two viruses, compared with 94% between different rabies virus strains within serotype 1. This comparison, extended to other unsegmented negative strand RNA viruses, gives new insight into the understanding of rhabdoviruses and paramyxoviruses. Furthermore, molecular cloning provides a rationale for the genetic engineering of a future vaccine.

[Antigenic variants of rabies virus isolated in the northeast and southeast of Brazil. Preliminary study]. / Variantes antigénicas del virus de la rabia aisladas en el nordeste y sudeste del Brasil. Estudio preliminar.

To help identify the different strains of rabies virus existing in Brazil, the antigenic profile of 13 virus isolates from humans and animals was determined. The indirect immunofluorescence technique was used, with monoclonal antibodies targeted at the viral nucleocapsid. In the northeast of the country five different viral strains were identified, and in the southeast, two. A rhabdovirus isolated from a fox could not be characterized as a rabies virus. Previously, only two antigenic variants had been identified in Brazil. It would appear that distribution of the strains is not related to the species from which they are isolated or to their geographical origin, a finding that differs from previous observations. These preliminary results underscore the need for further research in order to identify the existence and distribution of different strains of rabies virus in Brazil, which would help to prevent rabies vaccination failures.

Recent data on the epidemiology and prophylaxis of human rabies in France.

Rabies is an animal disease which is transmitted to man only by accident, most often through the bite (more rarely after scratches or licks of mucosa) of a rabid animal, domestic or wild. A good knowledge of the epizootiology of animal rabies is therefore necessary to establish, on solid grounds, the prophylaxis of human rabies. Inter-human transmission of rabies being an exceptional event which will be considered separately, the epidemiology of human rabies mainly studies the sources and circumstances of human exposure to rabid animals, which differ according to the epizootiology of animal rabies in a given country: either enzootic (or hyperenzootic) canine rabies, or enzootic selvatic rabies. It appears that the risk of human rabies is higher in the first situation for two reasons: (i) rabies viruses show an increased virulence due to numerous serial passages in dogs (viruses with short incubation period) and (ii) high frequency of dog-man contacts due to the high density of both populations.